Roughly chop the leftover roast chicken meat (including skin, if desired). You can make it as fine or chunky as you like.
Heat a frypan over medium heat, and saute the leeks and garlic in a bit of butter and olive oil until cooked down and tender, but not browned.
Add the flour, and stir for 1 minute until it coats the leeks.
Add in all the stock, and stir until well combined with the leek and the sauce starts to thicken a little.
Add in the chopped chicken and the thyme, and simmer until the gravy has thickened. The mixture should just hang on to a spoon before falling off.
Fit the shortcrust pastry sheets to your desired pie dish, making sure there are no holes. You may need to join several bits of pastry together.
Blind bake the pie crust by placing a sheet of baking paper over the raw pastry and filling it with pastry weights or uncooked rice. Bake for 15-20 minutes or until golden and cooked through.
Remove the baking paper and weights and add the filling. Place the puff pastry over the top and cut a cross in the centre to allow steam to escape. Ensure the edges are sealed to the pie base. Brush with milk or lightly beaten egg.
Bake for 30 minutes at 190C or until puff pastry is golden and cooked through.
Notes & Tips
Depending on how flavoursome your roast chicken meat is, you may want to add garlic and more fresh herbs to the mix. You could also add peas, corn kernals or any other vegies to the filling.